Contrary to the impression recent coverage may convey, there have actually been fewer U.S. child deaths in hot cars this year than at the same time in 2013.

"Last year on the 6th of July we had already had 20 and this year we have 15," Jan Null, a meteorologist who has tracked child heatstroke deaths for San Francisco State University since 1998, told USA TODAY Network.

The highest number of deaths occur in July and August, when there are an average of nine deaths each month, according to Null.

"That is what you would expect," he said. "Those are the two hottest months."

An average of 38 children die each year from vehicular heatstroke, according to Null's data. The highest death toll since he began tracking data occurred in 2010 when there were 49 deaths. In 2013, there were a total of 44.

However, both Rollins and Null warned that vehicular heatstroke deaths can occur in any month of the year.

"We try not to focus on one particular time because this can happen in any month and it can happen on days when it's as low as 60 degrees," Rollins said.

"People tend to dismiss this as a danger when they think that it only happens in the hot, Southern states," she added. "This year we had one in New York and on days when it really wasn't particularly hot outside," she said.

Twelve of this year's 15 deaths have been confirmed as caused by heatstroke. Three of them are still pending and waiting on official reports from medical examiners, according to Null. In all likelihood, those three will be also be deemed caused by vehicular heatstroke, Null said. Since 1998, all "probable" heatstroke deaths were ultimately confirmed by medical reports, he said.